Method for forming ultrafine particle brittle material at low temperature and ultrafine particle brittle material for use therein

ABSTRACT

A method for forming an ultrafine particle brittle material at low temperature which includes the steps of applying a mechanical impact force or a pressure to a ultrafine particle brittle material so as to have a percentage in the ultrafine particles having a primary particle diameter less than 50 nm in all the particles of 10 to 90%, subjecting the resulting brittle material to a heat treatment at a temperature not higher than the sintering temperature thereof so as to have the above percentage of 50% or less, and then applying a mechanical impact force not less than the crushing strength to the resultant material, to crush the material, thereby joining the ultrafine particles in the brittle material with one another, to form a formed article of the ultrafine particle brittle material; and an ultrafine particle brittle material for use in the method.

TECHNICAL FIELD

This invention relates to a technique for forming ultrafine particles ofa brittle material, such as ceramic material; that is, forming theparticles into a film or a formed article.

BACKGROUND ART

In a method for forming a brittle material at low temperature, usingmechanical impact force, such as a conventional aerosol depositionmethod (Jun Akedo: Oyo Buturi, Vol. 68, pp. 44-47, 1999; and Jun Akedo:Science and Industry, Vol. 76-2, pp. 1-7, 2002) described inJP-A-2001-3180, impact force is applied to raw material particles byparticle collision, the application of ultrasonic waves, or the like, soas to crush the particles, thereby forming newly generated faces, torealize bonds between the particles at low temperature. In this way, aformed article is yielded. By subjecting the raw material particles topre-treatment of applying mechanical impact force to the particles, witha mill or the like, at this time, so that the raw material particles canbe easily crushed by action of slight impact force, there is provided amethod in which internal energy is stored, in the form of defects ordislocations, in the raw material particles, and atom diffusion iseasily caused by slight stimulation from the outside, so that bondsbetween the particles can be realized at room temperature.

However, a low-temperature formed article of the brittle material formedin this way conversely contains a great number of defects ordislocations. When this method is applied to electronic material or thelike, electrical properties thereof are poorer than those of a materialfired at high temperature. Thus, problems remain that limit the scope towhich the method can be applied. If the mill treatment to which the rawmaterial particles are subjected before being formed is excessive,surfaces of the raw material particles excessively adsorb impurities,and defects are excessively introduced into the surfaces of the rawmaterial particles. Thus, the density of the formed film or formedarticle is also decreased. As a result, mechanical properties of thefilm or the formed article, such as the hardness and Young's modulethereof, are also decreased. Thus, problems remain in that practical usethereof is hindered.

DISCLOSURE OF THE INVENTION

The present invention is a method for forming an ultrafine particlebrittle material at low temperature, comprising steps of applying amechanical impact force or a pressure to the ultrafine particle brittlematerial so as to have a percentage in number of the ultrafine particlebrittle material particles having a primary particle diameter less than50 nm in all the particles of 10 to 90%, and further subjecting theultrafine particle brittle material to a heat treatment at a temperaturenot higher than the sintering temperature thereof so as to have apercentage in number of the ultrafine particle brittle materialparticles having a primary particle diameter less than 50 nm in all theparticles of 50% or less, and then applying a mechanical impact forcenot less than the crushing strength of the ultrafine particle brittlematerial to the resultant material, to crush the ultrafine particlebrittle material, thereby joining the ultrafine particles in the brittlematerial with one another, to form a formed article of the ultrafineparticle brittle material.

The present invention is also a ultrafine particle brittle material thathas a primary particle diameter of 50 nm or more, and that has, on thesurface thereof, no ultrafine particle brittle material particles havinga primary particle diameter of less than 50 nm.

Other and further features and advantages of the invention will appearmore fully from the following description, taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION Of THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the office upon request and paymentof the necessary fee.

FIG. 1 is a graph showing the relationship between the time for applyingmechanical impact force to raw material particles according to anembodiment of the present invention, and the film-forming speed in anaerosol deposition method.

FIGS. 2( a) to 2(d) are cross-sectional SEM photographs showing the timefor applying mechanical impact force to raw material particles that canbe used in the present invention, and the change in the micro-structureof films formed therefrom at room temperature.

FIGS. 3( a) to 3(d) are optical micrographs showing the time forapplying mechanical impact force to raw material particles that can beused in the present invention, and the change in the surface state offilms formed therefrom at room temperature.

FIG. 4 is a graph showing the relationship between the time for applyingmechanical impact force to raw material particles according to anembodiment of the present invention, and the Vickers hardness of PZTfilms produced by an aerosol deposition method.

FIGS. 5( a) to 5(d) are photographs showing the change in thetransparency of films formed at room temperature, depending on whetheror not raw material powder according to an embodiment of the presentinvention was subjected to heat treatment. FIG. 5( a) is a photograph ofthe surface of a film obtained when raw material particles subjected tono treatment (subjected to neither mechanical impact treatment nor heattreatment) were used; FIG. 5( b) is a photograph of the surface of afilm obtained when raw material particles subjected to only heattreatment were used; FIG. 5( c) is a photograph of the surface of a filmobtained when raw material particles subjected to mechanical impacttreatment (for 5 hours), followed by heat treatment, were used; and FIG.5( d) is a photograph of the surface of a film obtained when rawmaterial particles subjected to mechanical impact treatment (for 30hours), followed by heat treatment, were used. As to FIGS. 5( a) and5(b), when the photographs were taken, a support, which characters werewritten, was laid beneath the film, as a measure for transparency.

FIGS. 6( a) and 6(b) are graphs each showing a relationship between thepre-treatment effect of raw material particles according to anembodiment of the present invention, and the ferroelectricity of PZTfilms produced by an aerosol deposition method. FIGS. 6( a) and 6(b)respectively show results of a case of only mechanical impact forceapplying treatment, and results of a case of the combination ofmechanical impact force applying treatment with heat treatment.

FIGS. 7( a) to 7(c) are scanning electron microscopic (SEM) photographsobtained by photographing situations of raw material powders (PZT)according to an embodiment of the present invention after mechanicalimpact treatment. FIGS. 7( a), 7(b), and 7(c) show the raw materialpowders treated with a dry mill for 1 hour, 5 hours, and 30 hours,respectively.

FIGS. 8( a), 8(b), and 8(c) are scanning electron microscopic (SEM)photographs obtained by photographing the raw material powders of FIGS.7( a), 7(b), and 7(c), after the powders were treated with the dry milland subsequently heat-treated at 800° C. in the atmosphere for 4 hours,respectively.

FIGS. 9( a), 9(b), and 9(c) are scanning electron microscopic (SEM)photographs obtained by photographing sections of films formed from theraw material powders of FIGS. 8( a), 8(b), and 8(c), by an aerosoldeposition method, respectively.

FIGS. 10( a), 10(b), and 10(c) are scanning electron microscopic (SEM)photographs obtained by photographing the film-sections of FIGS. 9( a),9(b), and 9(c), with enlargement, respectively.

FIGS. 11( a) and 11(b) are transmission electron microscopic (TEM)photographs obtained by photographing raw material powder according toan embodiment of the present invention. FIG. 11( a) shows part of theperiphery of a raw material fine particle of lead zirconate titanate(PZT) after a dry mill treatment, as mechanical impact treatment, wasconducted for 5 hours, and FIG. 11( b) shows part of the periphery ofthe raw material fine particle after the particle was furtherheat-treated at 800° C. in the atmosphere for 4 hours.

BEST MODES FOR CARRYING OUT THE INVENTION

According to the present invention, the following means are provided.

-   (1) A method for forming an ultrafine particle brittle material at    low temperature, comprising the steps of applying a mechanical    impact force or a pressure to the ultrafine particle brittle    material so as to have a percentage in number of the ultrafine    particle brittle material particles having a primary particle    diameter less than 50 nm in all the particles of 10% to 90%, and    further subjecting the ultrafine particle brittle material to a heat    treatment at a temperature not higher than the sintering temperature    thereof so as to have a percentage in number of the ultrafine    particle brittle material particles having a primary particle    diameter less than 50 nm in all the particles of 50% or less    (preferably 0 to 50%), and then applying a mechanical impact force    not less than the crushing strength of the ultrafine particle    brittle material to the brittle material, to crush the ultrafine    particle brittle material, thereby joining the ultrafine particles    in the brittle material with one another, to form a formed article    of the ultrafine particle brittle material.-   (2) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the average    primary particle diameter of the ultrafine particle brittle    material, before the material is subjected to the mechanical impact    force or pressure-applying step, is from 50 nm to 5 μm.-   (3) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the temperature of    the heat treatment of the ultrafine particle brittle material is    from 200 to 1200° C.-   (4) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the heat treatment    of the ultrafine particle brittle material is performed in an    oxidizing atmosphere or a reducing atmosphere, such as hydrogen.-   (5) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the heat treatment    of the ultrafine particle brittle material is performed in a    reactive gas atmosphere.-   (6) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the time of the    heat treatment of the ultrafine particle brittle material is within    30 minutes.-   (7) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the application of    the mechanical impact force or the pressure to the ultrafine    particle brittle material is performed in a dry atmosphere (having a    water content of, e.g., 1% or less, preferably 0.5% or less).-   (8) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the forming step    is performed by an aerosol deposition method.-   (9) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein the application of    the mechanical impact force or the pressure to the ultrafine    particle brittle material is performed by means of a crusher.-   (10) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein, as the ultrafine    particle brittle material, an ultrafine particle brittle material    having a primary particle diameter of 50 nm or more, and having, on    the surface thereof, no ultrafine particle brittle material having a    primary particle diameter of less than 50 nm is used.-   (11) The method for forming the ultrafine particle brittle material    at low temperature described in item (1), wherein an ultrafine    particle brittle material having a polycrystal structure that is    made of microcrystals having a crystal grain diameter (crystallite    size) of 20 nm to 1 μm, and having a primary particle diameter of 50    nm to 5 μm is used.-   (12) The method for forming the ultrafine particle brittle material    at low temperature described in any one of items (1) to (11),    wherein, in the forming step, the ultrafine particle brittle    material, dried (to have a water content of, e.g., 1% or less,    preferably 0.5% or less) after the heat treatment, is mixed with a    gas (e.g. an inert gas, such as nitrogen, helium, or argon, and dry    air having a water content of 1% or less, preferably 0.5% or less),    and the mixture is blown through a nozzle onto a substrate, to crush    the ultrafine particle brittle material, thereby joining the    ultrafine particles in the brittle material with one another, to    form a formed article of the ultrafine particle brittle material.-   (13) An ultrafine particle brittle material that has a primary    particle diameter of 50 nm or more, and that has, on the surface    thereof, no ultrafine particle brittle material particles having a    primary particle diameter of less than 50 nm.-   (14) An ultrafine particle brittle material that has a polycrystal    structure which is made of microcrystals having a crystal grain    diameter (crystallite size) of 20 nm to 1 μm, and has a primary    particle diameter of 50 nm to 5 μm.

Herein, ultrafine particle brittle material particles having a primaryparticle diameter of less than 50 nm may be present independently ofeach other in the ultrafine particle brittle material, or they mayadhere or aggregate to the ultrafine particle brittle material having aprimary particle diameter of 50 nm or more. When the percentage innumber of ultrafine particle brittle material particles having a primaryparticle diameter of less than 50 nm in all the particles is 50% ormore, the whole is usually a green compact and is not solidified atambient temperature by an aerosol deposition method.

The primary particle diameter (size) is not equivalent to the crystalgrain diameter (crystallite size), and means the primary particlediameter of particles made of joined and compounded fine crystal grains.

The term “dried” means that the water content is usually 1% or less,preferably 0.5% or less, and it is preferable to remove physicaladsorption water so as to make the material into a state that onlychemical adsorption water (such as crystal water) is contained.

Additional preferable embodiments of the present invention are describedhereinafter; however, the present invention is not limited to them.

-   (15) The method for forming the ultrafine particle brittle material    at low temperature described in any one of items (1) to (12), or the    ultrafine particle brittle material described in item (13) or (14),    wherein the percentage in the number of the ultrafine particle    brittle material particles having a primary particle diameter less    than 50 nm in all the particles is 10% or less (preferably 0 to    10%), before the mechanical impact force or pressure-applying step.-   (16) The method for forming the ultrafine particle brittle material    at low temperature described in any one of items (1) to (12), or the    ultrafine particle brittle material described in item (13) or (14),    wherein the primary particle diameter of the ultrafine particle    brittle material is from 50 nm to 5 μm, before the mechanical impact    force or pressure-applying step; the primary particle diameter    thereof is from 20 nm to 1 μm, after the mechanical impact force or    pressure-applying step, and the primary particle diameter thereof is    from 80 nm to 5 μm, after the heat treatment.

(Herein, the ultrafine particle brittle material in item (16) refers toboth of the brittle material ultrafine particles present independentlyof each other, and the brittle material ultrafine particles adhering oraggregating with one another.)

-   (17) The method for forming the ultrafine particle brittle material    at low temperature described in any one of items (1) to (12), or the    ultrafine particle brittle material described in item (13) or (14),    wherein the thickness of a different layer (such as a contamination    layer or a surface defect layer) on the particle surface of the    ultrafine particle brittle material is from 3 to 5 nm, after the    mechanical impact force or pressure-applying step, and the thickness    of the different layer is 3 nm or less, after the heat treatment.-   (18) The method for forming the ultrafine particle brittle material    at low temperature described in any one of items (1) to (12), or the    ultrafine particle brittle material described in item (13) or (14),    wherein the particle diameters of secondary particles formed by    joining or binding the primary particles of the ultrafine particle    brittle material with one another range from 0.1 to 5 μm.-   (19) A method for forming an ultrafine particle brittle material at    low temperature, comprising the steps of applying a mechanical    impact to the ultrafine particle brittle material, to adjust the    crushability of the ultrafine particle brittle material and    mechanical properties thereof, such as the compressive strength    thereof, and further heat-treating the ultrafine particle brittle    material, at a temperature not higher than the sintering temperature    of the ultrafine particle brittle material, and subsequently joining    the ultrafine particle brittle material particles with one another,    so as to form a ultrafine particle brittle material formed product.

The crushability or the mechanical strength of the raw materialparticles depend on the diameter of the raw material particles and theamount of defects (stacking faults and plane defects), cracks, anddislocations introduced into the particles. Therefore, the wording“applying a mechanical impact to the ultrafine particle brittlematerial, to adjust the crushability of the ultrafine particle brittlematerial and mechanical properties thereof” referred to in item (19),means that the material is subjected to mechanical impact treatment soas to increase the particle diameter of the raw material and the amountof defects, cracks, and dislocations included inside the particles,thereby adjusting the crushability and mechanical properties insubsequent steps.

Hereinafter, the present invention is described in detail.

According to the present invention, in a method for forming a brittlematerial at low temperature using impact force, such as an aerosoldeposition method, mechanical impact force or pressure is beforehandapplied to brittle material ultrafine particles, which are raw materialparticles, by treatment with a crusher (mill) or the like, therebyadjusting the crushability and mechanical properties (for example, thecompressive strength, tensile strength, yield value, and elasticitylimit value) of the ultrafine particles in subsequent steps. After thistreatment of applying the mechanical impact force or the pressure isconducted or at the same time when the treatment is conducted, the rawmaterial particles are subjected to heat-treatment at a temperature nothigher than the sintering temperature of the raw material particles inan oxidizing atmosphere such as air or oxygen or in a reducingatmosphere such as hydrogen, thereby removing adsorbates, such as watermolecules, nitrogen molecules and extaneous materials, formed on thesurfaces of the ultrafine particles, so as to adjust the amount ofcracks, defects and dislocations introduced into the particles inaccordance with desired electrical properties. The two pre-treatmentsmake it possible to yield treated particles having characteristicssuitable for the above-mentioned method for forming brittle material atlow temperature. The treated particles are used to be subjected to anaerosol deposition method, thereby making it possible to yield a moldedproduct excellent in film-formability, formability, electricalproperties and mechanical properties. Specifically, in the presentinvention, before and after each of the first pre-treatment, in whichmechanical impact force or the like is applied, and the secondpre-treatment, which is heat treatment after the first pre-treatment,the particle sizes of the treated particles are adjusted, whereby themechanical properties of the treated particles can be adjusted. In otherwords, it is preferable that: before the first pre-treatment, the ratioof the number of the particles having a primary particle diameter ofless than 50 nm in that of all the particles before being crushed is 10%or less; after the crushing, which is the first treatment, the ratio ofthe number of the particles having a primary particle diameter of lessthan 50 nm in that of all the particles is from 10 to 90%; and after theheat treatment (the second pre-treatment) is further conducted after thecrushing treatment, the ratio of the number of the particles having aprimary particle diameter of less than 50 nm in that of all theparticles is 50% or less.

In the present invention, the forming the ultrafine particle brittlematerial at low temperature means that the used ultrafine particlebrittle material is formed at a temperature lower than the sinteringtemperature of the material. The sintering starting temperature dependson not only the composition of the brittle material but also the primaryparticle diameter thereof. The method of the present invention can beperformed at a lower temperature than this sintering startingtemperature.

The mechanical impact force applying treatment as this pre-treatmentstep (the first pre-treatment) is performed in order not to make rawmaterial particles minute but to increase internal energy accumulated inthe form of defects or dislocations inside the microcrystal whichconstitutes the raw material particles by the application of themechanical impact force, so as to decrease the impact force or pressurewhich is applied, at the time of forming the particles into a film orforming the particles in a subsequent step, in order to crush thebrittle material ultrafine particles, thereby making the crushing of theparticles easy at the time of the film-formation or the forming. It istherefore preferred that the power and time for applying the mechanicalimpact force in the first pre-treatment are adjusted so that the rawmaterial particles will not be made minute by excessive crushing orpulverizing. It is unnecessary that the magnitude of the mechanicalimpact force or pressure applied in the first pre-treatment is madelarger than the crushing strength of the brittle material ultrafineparticles.

Thereafter, the particles are subjected to heat treatment, for example,treatment with an electric furnace in the atmosphere for 30 minutes to10 hours, as one of the pre-treatment steps (the second pre-treatment).The particles are then formed into a film or a formed article by, forexample, an aerosol deposition method. The heat treatment temperature atthis temperature is a temperature at which the raw material particlesare not sintered. Namely, the raw material particles are heat-treated ata temperature not higher than the sintering temperature of theparticles. In general, the sintering temperature of ceramics or the likeis 1000° C. or higher, and molecules of water and others, which areeasily adsorbed on surfaces of particles exposed to the atmosphere, canbe removed at 200° C. or higher. Accordingly, the heat treatmenttemperature is preferably from 200 to 1200° C., considering a largereduction in defects of the surfaces of the raw material particles, andthe temperature is more preferably from 600 to 1000° C., consideringthat chemical adsorption water also is sufficiently removed. However,about the heat treatment time, the heat treatment for a long time maycause bonding between the particles to advance by ordinary sinteringreaction, dependently on the raw material, when the heat treatmenttemperature is raised to 1000° C. or higher in order to attain a largedecrease in surface defective layers and the like of the raw materialparticles. It is therefore preferred that when the heat treatment isconducted at such a high temperature, the treatment is conducted in aheat treatment time of 30 minutes or less. Alternatively, the mechanicalimpact force or pressure applying treatment and the heat treatment maybe simultaneously conducted.

The surrounding atmosphere in the heat treatment step is not limited tothe atmosphere (the air), and may be appropriately selected into anoxidizing or reducing atmosphere, a reactive gas atmosphere, or thelike, dependently on electrical properties of a target brittle material(an oxide, nitride, carbide, semiconductor or the like). When thetreatment is conducted in a reducing atmosphere wherein hydrogen ispresent, it is possible that: excessive oxygen, which is physically orchemically absorbed at an originally excessive amount on commerciallyavailable raw material particles, is adjusted to attain idealcomposition-control; the electric resistance and others of the oxide arelargely changed; and when the brittle material particles are mixed withmetal particles or the like and the mixture is formed into a film or aformed article, the oxidization of the surface of the metal is preventedso as to give superior properties.

Hereinafter, examples of embodiments according to the present inventionare described with reference to the drawings.

Examples of the brittle material which is used as raw material particlesin the present invention include lead zirconate titanates (such as PZTand PLZT), which are piezoelectric materials, wherein various admixturesare incorporated, barium titanate (BTO), ferrites wherein variousadmixtures are incorporated (such as NiZn ferrite, MnZn ferrite, MgMnferrite, NiZnCu ferrite, NiZnCo ferrite, BaFe₁₂O₁₉ and SrFe₁₂O₁₉ whichare M type ferrites, BaFe₁₈O₂₇, which is a BaFe₂W type ferrite,Ba₃Co₂Fe₂₄O₄₁, which is a Co₂-Z type ferrite, Ba₂Zn₂Fe₁₂O₂₂, which is aZn₂-Z type ferrite, α-Fe₂O₃, β-Fe₂O₃, and γ-Fe₂O₃), alumina (α-Al₂O₃),titania, zirconia (YSZ and ZrO₂), SiO₂, MgB₂, CeFe₂, CoO, NiO, MgO,silicon nitride, aluminum nitride, silicon carbide, apatites (variousapatite type minerals such as hydroxyapatite(HAp)), oxide typesuperconductors (such as Y—Ba based oxide superconductors, Bi—Sr—Cabased oxide superconductors, and Tl—Ba—Ca based oxide superconductors),and semiconductor materials (such as Si, Ga and GaN).

These raw materials were used and molded into a film form at ambienttemperature by an aerosol deposition method, which is afilm-forming/forming method using impact force, after a pre-treatmentwhich will be described later.

The aerosol deposition method is typically a method of mixing dry powderwith a gas (for example, an inert gas such as nitrogen, helium, orargon, and dry air having a water content of 1% or less, preferably 0.5%or less), blowing the mixture onto a substrate through a nozzle inside areduced pressure chamber to crush the raw material particles into adiameter of 50 nm or less, and forming the crushed particles into a filmor a formed article to have a density of 95% or more of the theoreticaldensity. In the method of the present invention, as the aerosoldeposition method, a known method can be used. For example, a methoddescribed in the above-mentioned JP-A-2001-3180 or the like can be used.The JP-A-2001-3180 is incorporated herein for reference. According tothe aerosol deposition method, the brittle material ultrafine particlesare joined with one another and further some parts of the ultrafineparticles can be joined with the substrate.

The film-forming/forming of the aerosol deposition method was performedat a particle velocity of 30 to 500 m/sec under a reduced pressure of 10Torr or less. As the raw material particles, various particles having anaverage primary particle diameter of 50 nm to 5 μm were used. As thesubstrate onto which the raw material particles were blown by theaerosol deposition method, there were used various substrate, such as aSi wafer, stainless steels (SUS304, 316 and so on), quartz glass, aquartz wafer, and plastics (such as acrylonitrile-butadiene-styreneresin (ABS), polyethylene terephthalate (PET), polytetrafluoroethylene(PTFE), polyimide, polymethyl methacrylate (PMMA), epoxy resin,polystyrene, vinyl resin, polycarbonate, and polypropylene).

In the mechanical impact force or pressure applying treatment, the rawmaterial particles were subjected to mechanical impact force applyingtreatment with a planetary mill (PM-1200 or MT-100 (trade name)manufactured by Seishin Enterprise Co., Ltd.). It appears that thiswould make it possible to crush the brittle material ultrafine particlesin a subsequent film-forming/forming step.

This mechanical impact force applying treatment with the mill is not anytreatment for making the raw material particles minute but is atreatment for increasing internal energy accumulated in the form ofdefects or dislocations inside the raw material particles by theapplication of the mechanical impact force, so as to decrease the impactforce or pressure which is applied, at the time of forming the particlesinto a film or a formed article. Accordingly, the power and time forapplying the mechanical impact force are adjusted so that the rawmaterial particles will not be made minute by excessive crushing orpulverizing.

In the present embodiment, as such a mechanical impact force applyingtreatment, the following pre-treatment was conducted: a treatment inwhich zirconia, alumina or stainless steel balls, which had a diameterof 3 mm or more, and the raw material particles were put into azirconia, alumina or stainless steel pot and then the pot was fitted toa crusher such as a planetary mill, vibration mill, ball mill, attractormill or dyno mill in a dry state, in which water or any other solvent isnot used, at a rotational speed of 50 to 300 rpm (applied acceleration:1 G or more) for 10 minutes to 30 hours. If the mechanically-impactingtreatment (the first pre-treatment) of the raw material particles(powder) is performed by wet pulverization, the raw material powder isexcessively made minute by the invasion of solvent (water, alcohol orthe like) onto the surface of the particles or inside cracks therein sothat the above-mentioned desired particle-size-adjustment may not beattained. It is therefore preferred that the raw material particles areset to a crusher under a dry condition. It is preferred that therelative humidity at this time is controlled into 50% or less.

Thereafter, an electric furnace was used to conduct heat treatment inthe atmosphere for 30 minutes to 10 hours as one of the pre-treatments.Thereafter, film-forming or forming was performed by the above-mentionedaerosol deposition method. The heat treatment at this time is atemperature at which the raw material particles are not sintered.Namely, the film-forming or forming is performed at a temperature nothigher than the sintering temperature of the raw material particles. Ingeneral, the sintering temperature of ceramics or the like is 1000° C.or higher, and molecules of water and others, which are easily adsorbedon surfaces of particles exposed to the atmosphere, can be removed at200° C. or higher. Accordingly, the heat treatment temperature ispreferably from 200 to 1200° C., considering a large reduction indefects of the surfaces of the raw material particles, and thetemperature is more preferably from 600 to 1000° C., considering thatchemical adsorption water also is sufficiently removed. However, aboutthe heat treatment time, the heat treatment for a long time may causebonding between the particles to advance by ordinary sintering reaction,dependently on the raw material, when the heat treatment temperature israised to 1000° C. or higher in order to attain a large decrease insurface defective layers and the like of the raw material particles. Itis therefore preferred that when the heat treatment is conducted at sucha high temperature, the treatment is conducted in a heat treatment timeof 30 minutes or less.

The surrounding atmosphere in the heat treatment step is not limited tothe atmosphere (the air), and may be appropriately selected into anoxidizing or reducing atmosphere, a reactive gas atmosphere, or thelike, dependently on the electrical property of a target brittlematerial (an oxide, nitride, carbide, semiconductor or the like). Whenthe treatment is conducted in a reducing atmosphere wherein hydrogen ispresent, it is possible that: excessive oxygen, which is physically orchemically absorbed at an originally excessive amount on commerciallyavailable raw material particles, is adjusted to attain idealcomposition-control; the electric resistance and others of the oxide arelargely changed; and when the brittle material particles are mixed withmetal particles or the like and the mixture is formed into a film or aformed article, the oxidization of the surface of the metal is preventedso as to give superior properties.

The ultrafine particle brittle material formed product obtainedaccording to the method of the present invention may be furthersubjected to heat treatment. The molded product made of, for example, aferroelectric and piezoelectric material such as PZT (lead zirconatetitanate) or BTO (barium titanate), a ferromagnetic material or anelectroconductive ceramic is subjected to the heat treatment after theforming, whereby the electrical properties thereof can be furtherimproved. As such heat treatment after the forming step, heat treatmentwhich is usually conducted in the art can be used. For example, leadzirconate titanate (PZT) is subjected to heat treatment in theatmosphere at 600 to 900° C. for 10 minutes to 1 hour, and bariumtitanate (BTO) is subjected to heat treatment in the atmosphere at 600to 1200° C. for 10 minutes to 1 hour, whereby desired electricalproperties (piezoelectricity and ferroelectricity) can be improved.

The following describes the ultrafine particle brittle material of thepresent invention.

It is preferable to use, as the ultrafine particle brittle material inthe method of the present invention, a ultrafine particle brittlematerial which has a primary particle diameter of 50 nm or more,preferably 80 nm to 5 μm and has, on the surface thereof, no ultrafineparticle brittle material particles having a primary particle diameterof less than 50 nm, preferably less than 20 nm.

In the present invention, the crushing strength of raw material of theultrafine particle brittle material is adjusted by mechanical impactforce or pressure applying treatment (such as dry mill treatment). Sincethe crushability or mechanical strength of the raw material particlesdepend on the particle diameter of the raw material particles and theamount of defects (stacking faults and plane defects), cracks anddislocations included in the particles, this mechanical impact force orpressure applying treatment is effective.

In actual treatment, however, it is difficult that cracks, dislocations,defects and others are included in the raw material particles withoutgenerating any crushed particles having a primary particle diameter ofless than 50 nm in the particles. The ultrafine particle brittlematerial having a primary particle diameter of less than 50 nm, which ispulverized or crushed by the first pre-treatment (or is originallycontained), turns into the state that the material adheres or aggregateson the surface of ultrafine particle brittle material which is notcrushed or pulverized and has adjusted crushing strength and a primaryparticle diameter of 50 nm or more. For example, as illustrated in FIGS.7( a) to 7(c), in the raw material particles subjected to dry milltreatment, ultrafine fine particles having a primary particle diameterof less than 50 nm adhere or aggregate on the surfaces of ultrafineparticles having a primary particle diameter of 50 nm or more, or arepresent independently of ultrafine particles having a primary particlediameter of 50 nm or more.

It appears that when such raw material particles are, as they are,formed a formed article or a film, the crushed or pulverized ultrafineparticle brittle material having a primary particle diameter of lessthan 50 nm functions as a cushion for absorbing impact. Thus, subsequentcrushing or activation of the particles is not sufficiently caused. As aresult, the film density of the resultant formed product/film lowers sothat high film hardness or superior electrical properties may not beobtained.

On the other hand, when the above-mentioned heat treatment is conductedas the second pre-treatment after the mechanical impact or pressureapplying treatment (the first pre-treatment), the ultrafine particlebrittle material which is crushed or pulverized by the firstpre-treatment and has a primary particle diameter of less than 50 nm canbe extinguished by the growth or recombination of the particles. Asituation that the particles grow slightly at the time of thisextinction was observed with a scanning electron microscope (SEM). Forexample, each of the raw material powders illustrated in FIGS. 7( a),7(b) and 7(c) was subjected to dry mill treatment followed by heattreatment for 1 hour, 5 hours and 30 hours. As a result, as shown inFIGS. 8( a), 8(b) and 8(c), the ultrafine particle brittle materialhaving a primary particle diameter of less than 50 nm, which adhered oraggregated onto the surfaces of the ultrafine particles having a primaryparticle diameter of 50 nm or more, or which was mixed with theultrafine particles having a primary particle diameter of 50 nm or more,became extinct so that the particles grew slightly as a whole. Theseultrafine particles subjected to the heat treatment were used to form afilm by an aerosol deposition method. As a result, very dense films wereobtained as shown in FIGS. 9( a), 9(b) and 9(c) as sectional SEMphotographs and 10(a), 10(b) and 10(c) as enlarged sectional SEMphotographs.

After this first pre-treatment step (mechanical impact applyingtreatment), the second pre-treatment step (heat treatment) is performed,thereby making it possible to yield raw material ultrafine particleshaving a preferable particle diameter range and having therein defects(stacking faults or plane defects) or cracks.

The highest temperature or time in the heat treatment step of the secondpre-treatment are also decided in accordance with relationship with theabove-mentioned first pre-treatment. If the heat treatment is conductedat a temperature close to the sintering-starting-temperature for a verylong time, atom diffusion increases by heat so that different layers(such as a contamination layer or a surface defect layer) on thesurfaces of the raw material particles decrease. However, the defects(stacking faults or plane defects), cracks and dislocations which areformed in the first pre-treatment step and included in the raw materialparticles also become extinct. For this reason, mechanical properties ofthe raw material particles, such as the compressive strength thereof,are improved. Consequently, it cannot be expected that the film-formingspeed and the formability are improved although the denseness andelectrical properties of the film are improved. Accordingly, the firstpre-treatment, wherein mechanical impact force is applied to the rawmaterial particles, and the second pre-treatment, which is based on heattreatment, produce conflicting effects on the raw material particles.However, it is preferred that respective conditions are adjusted andbalanced in such a manner that high moldability and film-forming speedcan be compatible with good film density and electrical properties inaccordance with the material property of the raw material particles.

In the second pre-treatment step based on the heat treatment, theprimary particles are recombined so that secondary particles are alsoformed. If the heat treatment is excessive at this time, therecombination advances so that the secondary particles become too large.As a result, etching acts when the particles are formed into a film.Thus, properties of the film may be adversely affected. Accordingly, thesize of the secondary particles, which result from the recombination inthe heat treatment, preferably ranges from 0.1 to 5 μm. It is preferredto adjust the heat treatment temperature and the heat treatment time inthis case so as to set the second particle diameter into this range.

By the above-mentioned heat treatment (the second pre-treatment), anydefect layer on the raw material powder surface, any contamination layerbased on the adsorption of water content or atmospheric gas, and anydefect layer on the surfaces of the particles are removed so thatelectrical properties of the film/formed article can be improved. Forexample, on the surfaces of the raw material particles, a differentlayer having a thickness of 3 to 5 nm was observed after the mechanicalimpact or pressure applying treatment (the first pre-treatment) (FIG.11( a)). The thickness of this different layer became 3 nm or less afterthe heat treatment (the second pre-treatment) (FIG. 11( b)). This matterwas observed from a transmission electron microscopic image (TEM image).In FIG. 11( b), a 3-mm thick portion outside the periphery of one out ofthe PZT particles is the different layer.

In this way, the first pre-treatment step (mechanical impact treatment)and the second pre-treatment step (heat treatment) are appropriatelyadjusted, thereby making it possible to yield a ultrafine particlebrittle material having a polycrystal structure which has a primaryparticle diameter of 50 nm to 5 μm and is made of microcrystals having acrystal grain diameter (crystallite size) of 20 nm to 1 μm. When thisultrafine particle brittle material having the polycrystal structure isformed into a film form, a film having superior electrical propertiescan be obtained at a high film-forming speed. In such ultrafineparticles having the polycrystal structure, which are different fromsecondary particles obtained by the aggregation or adhesion of primaryparticles, microcrystals thereof are joined with one another withoutcontaining any different layer (such as a contamination layer or asurface defect layer); therefore, electrical properties of thefilm/formed article obtained from this are very good. Such fineparticles having the polycrystal structure have a lower mechanicalstrength than monocrystal structure particles having the same particlediameter; therefore, they are easily crushed from joint faces betweenthe crystal particles as starting points. Thus, they are excellent infilm-forming speed and formability in aerosol deposition method. Thismatter has been found out by the inventors.

The second pre-treatment together with the first pre-treatment isconducted in this way, whereby the particles are sufficiently crushed oractivated by collision between the particles in a subsequent formingstep. As a result, a dense and superior molded product, such as a film,having a high film hardness and superior electrical properties can beobtained.

Such raw material particles, which are subjected to mechanical impact orpressure applying treatment and heat treatment, are very effective, asraw material powder for a forming step such as an aerosol depositionmethod, for yielding a good film quality regardless of the materialproperty of the brittle material.

FIG. 1 is a graph showing difference between film-forming speed in thecase that PZT raw material particles were subjected to mechanical impactforce applying treatment as the above-mentioned pre-treatment for 0, 1,5 and 30 hours and film-forming speed in the case that the particleswere subjected to the above-mentioned heat treatment alone or thecombination of the heat treatment with the mechanical impact force orpressure applying treatment.

FIGS. 2( a) to 2(d) are sectional SEM (scanning electron microscope)photographs showing change in the micro-structure of films produced fromparticles to which various pre-treatment conditions were applied in theabove-mentioned pre-treatment step, that is, particles to which themechanical impact force was applied for 0 hour (FIG. 2( a)), 1 hour(FIG. 2( b)), 5 hours (FIG. 2( c)) and 30 hours (FIG. 2( d)).

FIGS. 3( a) to 3(d) show change in optical micrographs observed fromsurfaces of films produced from particles to which various pre-treatmentconditions were applied in the above-mentioned pre-treatment step, thatis, particles to which the mechanical impact force was applied for 0hour (FIG. 3( a)), 1 hour (FIG. 3( b)), 5 hours (FIG. 3( c)) and 30hours (FIG. 3( d)).

Furthermore, FIG. 4 shows change in the Vickers hardness of filmsproduced under various pre-treatment conditions in the above-mentionedpre-treatment step. The Vickers hardness was measured with DUH-201W((trade name) manufactured by Shimadzu Corporation).

FIGS. 5( a) to 5(d) show results obtained by observing by the opticalmicroscope difference in the transparency, surface state and others ofthe film before and after heat treatment was introduced in theabove-mentioned pre-treatment.

FIGS. 6( a) and 6(b) show electrical properties (residual polarizationand the hysteresis characteristic of the electric field applied:ferroelectricity) of PZT films produced under the above-mentionedvarious conditions in the above-mentioned pre-treatment step. About themeasured samples, the raw material particles subjected to theabove-mentioned pre-treatment were formed into films on metal substratesmade of stainless steel or the like at room temperature, without heatingthe substrate, by an aerosol deposition method. Thereafter, the filmswere subjected to heat treatment in the air for 1 hour and then measuredwith a hysteresis characteristic evaluating device (TF-ANALYZER 2000(trade name) manufactured by Aix ACCT Co.).

According to FIG. 1, when the raw material particles are subjected toonly the mechanical impact force applying treatment, the film-formingspeed (represented by gray bars in the figure) in the aerosol depositionmethod is remarkably increased with an increase in the time for thetreatment; and by the treatment for 5 hours, the speed reaches a value(73 μm/min.) about 30 times larger than that in the case that rawmaterial particles not subjected to the above-mentioned pre-treatmentare used. However, it is understood that when the treatment is conductedfor a longer time than it, the film-forming speed is conversely lowered.This would be because the mechanical impact force applying treatmentover the excessively long time causes adsorption of water molecules,impurities or others onto the surfaces of the raw material particles.

It is understood from the SEM photographs (section observation) of FIGS.2( a), 2(b), 2(c) and 2(d) that: in the case that no heat treatment isconducted as the pre-treatment step of the raw material particles, thedensity of the film falls as the treatment time for applying themechanical impact force to the raw material particles increases; and thefilm density becomes 90% or less of the theoretical density by thetreatment for about 5 hours.

It is understood from the optical microscopic photographs (surfaceobservation of the films) of FIGS. 3( a), 3(b), 3(c) and 3(d) that asthe treatment time for applying the mechanical impact force to the rawmaterial particles increases, the film is changed from a semitransparentyellow state to a white opaque state. This is because the film densityfalls to increase light scattering as the time for applying themechanical impact force to the raw material particles increases.

About change (-Δ-) in the Vickers hardness of the film shown in FIG. 4,the hardness falls as the treatment time for applying the mechanicalimpact force increases. This is also explained by the fall in the filmdensity.

As described above, the effect of the pre-treatment based on mechanicalimpact force application makes the film-forming speed about 30 timesbetter, and is excellent. However, the effect simultaneously makes thefilm density low. Thus, a problem has been made clear that use asfilm-forming/forming technique is restricted dependently on the usepurpose thereof.

Next, results in the case that the heat treatment is conducted togetherwith the pre-treatment step based on the mechanical impact forceapplication are observed. About the change in the film-forming speed ofFIG. 1, in the case that only the heat treatment is applied (a black barat zero h), the speed is made about 2 times larger than in the case thatno treatment is conducted (a gray bar at zero h in FIG. 1). When theabove-mentioned heat treatment is applied to the raw material particlessubjected to the pre-treatment of the mechanical impact forceapplication (a black bar at 5 h), the film-forming speed is made lowerthan in the case that only the mechanical impact force applyingtreatment is conducted, but the film-forming speed is made 6-10 timeslarger than in the case that the raw material particles subjected to notreatment is used. Furthermore, according to an increase in the Vickershardness of FIG. 4 (-◯- in the figure) and an improvement in thetransparency shown in FIGS. 5( c) and 5(d) at this time, the density ofthe film is improved and is restored to the same level as in the case ofthe raw material particles subjected to no treatment (-◯- at 0 h in FIG.4, and FIG. 5( a)).

It is therefore understood that the pre-treatment step based on theabove-mentioned mechanical impact force application and theabove-mentioned heat treatment are used together as pre-treatment stepsfor raw material particles of a brittle material fine particlelow-temperature forming method, whereby high film-forming speed andformability and superior film density can be simultaneously realized sothat superior mechanical properties can be obtained.

Hereby, mechanical impact or pressure applying treatment applied to theraw material particles and heat treatment at not higher than thesintering temperature are appropriately combined with each other andadjusted, whereby the density, porosity and mechanical properties of thefilm/molded product formed by use of impact force in an aerosoldeposition method or some other method can be arbitrarily controlled.

Next, observed is a change in electrical properties, in particular, theferroelectricity (residual polarization and the hysteresis property ofthe electric field applied) in a case in which PZT raw materialparticles of raw particles were subjected to mechanical impact forceapplying treatment as the above-mentioned pre-treatment step and theabove-mentioned heat treatment step independently of each other or thecombination thereof. FIG. 6( a) is about a case in which only thepre-treatment step based on the mechanical impact force application wasconducted. It is understood that the residual polarization (Pr: theintercept between each hysteresis curve and the vertical axis) becomeslower as the treatment time becomes larger. In general, aboutferroelectric material and piezoelectric material, such as PZT,electrical properties thereof are decided by the magnitude of theresidual polarization thereof. As this value is larger, the material hasbetter electrical properties. Accordingly, in the case that only thepre-treatment step based on the mechanical impact force application isconducted, the electrical properties lower. It appears that one reasonfor this is that the density of the thus-produced film is low.

In the meantime, a case in which the above-mentioned heat treatment isapplied to raw material particles subjected to the pre-treatment stepbased on the mechanical impact force application is shown in FIG. 6( b).In the heat treatment at this time, raw material particles subjected tothe pre-treatment based on the mechanical impact force application andthose subjected to no pre-treatment were separately subjected to heattreatment at 800° C. in the atmosphere for 4 hours. As a result, it isunderstood that: when the heat treatment step was applied to the rawmaterial particles, the residual polarization increased drastically; andeven in the case that the pre-treatment step based on the mechanicalimpact force application for 5 hours was conducted, the residualpolarization value as an electrical property was made better from 20μC/cm² to 32 μC/cm² than in the case that the raw material particlessubjected to no treatment were used. The residual polarization value inthe case that the pre-treatment step based on the mechanical impactforce application for 5 hours was conducted was substantially equivalentto that in the case that the raw material particles were subjected toonly the heat treatment step. It is understood from this that a highfilm-forming speed resulting from the pre-treatment step based on themechanical impact force application can be maintained.

Next, the reason why such an improvement in the electrical properties ismade is analyzed from the viewpoint of raw material composition.

TABLE 1 Relationship between the pre-treatment effect of raw materialparticles and the raw material composition of each PZT film produced byan aerosol deposition method Impact treatment time (h) Ratio betweennumbers Content of the of atoms pre-treatment for (ZR + Ti)/ rawmaterial particles Zr/Ti Pb O/Pb Case of only mechanical 0 1.08 0.991.41 impact treatment 5 1.085 1.02 1.43 30 1.09 1.03 1.45 Case of thecombination 0 1.09 1.01 1.56 of mechanical impact 5 1.08 1.01 1.51treatment and heat treatment Bulk of PZT 1.0889 1.0 1.5

Table 1 shows results obtained by subjecting PZT raw material particles,which are raw material particles, to mechanical impact force applyingtreatment as the above-mentioned pre-treatment step and theabove-mentioned heat treatment step independently of each other or incombination thereof, forming PZT films by an aerosol deposition method,subjecting the PZT films to heat treatment at 600° C. in the atmospherefor 1 hour, and subsequently comparing the composition distributions ofthe PZT films with the material composition of a bulk produced by aconventional sintering method (sintering conditions: 125° C. for 2hours). For the analysis of the compositions, a fluorescent X-rayanalyzer (ZSX 100e (trade name) manufactured by Rigaku Co.) was used.About all samples under the treatment conditions, ratios in the metalcomposition (lead, zirconium and titanium) thereof were not largelychanged from those of the bulk. In the case that only the mechanicalimpact force applying treatment was conducted as the above-mentionedpre-treatment step, the oxygen composition was lower than in the case ofthe bulk material. It appears that this causes the above-mentioned fallin the residual polarization value as well as fall in the density. Onthe other hand, when the above-mentioned heat treatment was conductedtogether, all the material composition ratios, including the oxygencomposition ratio, were sufficiently consistent with the materialcomposition ratios in the bulk. Thus, it has been made clear that idealmaterial composition control can be attained.

Therefore, it has been made clear that the pre-treatment step based onthe mechanical impact force application and the heat treatment step areused together with each other as pre-treatment steps for raw materialparticles of a brittle material fine particle low-temperature formingmethod, thereby making it possible to realize high film-forming speedand formability, an excellent film density, and an ideal materialcomposition simultaneously so as to yield excellent electricalproperties.

As described above, according to the present invention, thepre-treatment step based on the mechanical impact force application andthe heat treatment step are used together with each other aspre-treatment steps for raw material particles of a brittle materialfine particle low-temperature forming method, thereby making it possibleto realize high film-forming speed and formability, an excellent filmdensity, and an ideal material composition simultaneously so as to yieldexcellent electrical properties.

In particular, according to the present invention, raw materialparticles preferably having an average primary particle diameter of 50nm to 5 μm are subjected to heat treatment at the sintering temperatureor lower of 200 to 1200° C., more preferably 600 to 1000° C., therebymaking it possible to realize high film-formability and formability andstrong bonds between the raw material particles and to provide a formingmethod for forming a film or a shaped product having a high density, amechanical property of a high strength, and electrical properties closeto those of a bulk obtained by firing at high temperature withoutapplying any heat at the time of forming the film or shaped product.

INDUSTRIAL APPLICABILITY

The method of the present invention is suitable as a method for forminga ultrafine particle brittle material having good electrical propertiesuseful as electronic material such as ferroelectric material orpiezoelectric material or for forming the material into a film at a lowtemperature which is lower than the sintering temperature of thematerial.

According to the ultrafine particle brittle material of the presentinvention, for example, a ceramic film having controlled density andmechanical strength can be formed on a metal material or a plasticmaterial. It is therefore possible to apply this material to the usefield of a corrosion-resistant or abrasion-resistant coat, a ceramicfilter, an insulating film or the like.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

1. A method for forming an article from an ultrafine particle brittle materials, comprising the steps of: applying a mechanical impact force or a pressure to the ultrafine particle brittle material so as to have 10% to 90% in number of all the resultant ultrafine particle brittle material particles have a primary particle diameter less than 50 nm; subjecting the ultrafine particle brittle material to a heat treatment at a temperature in the range of from 200 to 1200° C. that is not higher than the sintering temperature thereof, wherein the heat treatment of the ultrafine particle brittle material particles having a primary particle diameter less than 50 nm extinguishes or reduces the number of said particles to 50% or less in the heat-treated ultrafine particle brittle material; and then applying a mechanical impact force not smaller than the crushing strength of the ultrafine particle brittle material to the heat-treated ultrafine particle brittle material by means of particle collision for generating crushed faces on the crushed ultrafine particle brittle material, thereby joining the individual resultant particle brittle materials together to form said article made of the ultrafine particle brittle material.
 2. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the average primary particle diameter of the ultrafine particle brittle material, before the material is subjected to the first mechanical impact force or pressure applying step, is from 50 nm to 5 μm.
 3. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the heat treatment of the ultrafine particle brittle material is performed in an oxidizing atmosphere or a reducing atmosphere.
 4. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the heat treatment of the ultrafine particle brittle material is performed in a reactive gas atmosphere.
 5. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the time of the heat treatment of the ultrafine particle brittle material is within 30 minutes.
 6. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the application of the mechanical impact force or the pressure to the ultrafine particle brittle material is performed in a dry atmosphere.
 7. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the step of joining individual resultant particle brittle materials is performed by an aerosol deposition method.
 8. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the application of the mechanical impact force or the pressure to the ultrafine particle brittle material is performed by means of a crusher.
 9. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein, as the ultrafine particle brittle material, ultra fine particle brittle material particles having a primary particle diameter of 50 nm or more, and having, on the surface thereof, no ultrafine particle brittle material particles having a primary particle diameter of less than 50 nm is used.
 10. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein, as the ultrafine particle brittle material, ultrafine particle brittle material particles having a polycrystal structure that is made of microcrystals having a crystal grain diameter of 20 nm to 1 μm, and having a primary particle diameter of 50 nm to 5 μm is used.
 11. The method for forming the article from the ultrafine particle brittle material according to anyone of claims 1 to 10, wherein the ultrafine particle brittle material, dried after the heat treatment, is mixed with a gas, and the mixture is blown through a nozzle onto a substrate, to crush the ultrafine particle brittle material, thereby joining the ultrafine particles in the brittle material with one another, to form the ultrafine particle brittle material article.
 12. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the ultrafine particle brittle material is a ceramic material.
 13. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the ultrafine particle brittle material is selected from the group consisting of an oxide, nitride, carbide and semiconductor material.
 14. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the ultrafine particle brittle material used for said step of applying the mechanical impact force or a pressure is selected from the group consisting of lead zirconate titanates, barium titanate, ferrites, alumina, titania, zirconia, SiO₂, MgB₂, CeFe₂, CoO, NiO, MgO, silicon nitride, aluminum nitride, silicon carbide, apatites, oxide type superconductors and semiconductor materials.
 15. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the formed article is a film.
 16. The method for forming the article from the ultrafine particle brittle material according to claim 1, wherein the formed article has a density of 95% or more of the theoretical density. 